Application of geothermo-barometers to Mesozoic granitoids in the Jiaodong Peninsula, eastern China: Criteria for selecting methods of pressure estimation and implications for crustal exhumation

摘要

The Mesozoic lithospheric destruction of the North China Craton (NCC) in eastern China with a concomitant large-scale crustal exhumation has been widely accepted. However the specific timing, magnitude and rate of exhumation remain elusive. The widely outcropping episodes of Mesozoic granitoids in the Jiaodong Peninsula provide an excellent natural case for crustal exhumation research. Application and comparison of two Al-inhornblende barometers and experimental Qz-Ab-Or phase diagram indicate that oxygen fugacity could affect pressure estimation of granitoids and the Al-in-hornblende barometers derived from the AS95 (referring to Anderson and Smith, 1995) has the potential to estimate pressures of granitoids emplaced at 1-2 kbar. The QzAb-Or phase diagram can be used to constrain the emplacement pressures of granitoids on the premise of selecting suitable geochemical data. Our results demonstrate a rapid crustal exhumation event between similar to 160 and 115 Ma, i.e., approximately 10 km for the Jiaobei terrane and 7 km for the ultra-high pressure metamorphic terrane, reflecting heterogeneous exhumation possibly in response to the lithospheric destruction of the NCC.